Re: Topband: cutting coax stubs for 80 meter 4-square
Hi guys and gals, Well, to make a long story short my Rig Experts AA-170 has quite working. Looks normal but a 56 ohm resistor at the end of the 75 ohm coax reads infinite. On the MFJ-259b it reads 56 ohms. Check SWR and the MFJ reads 7.499.2 Mhz 1.1:1 SWR R=56/57 ohms X=0. Coax is 55' 4 3/8" long when I got very near 7500 KHz. With the shorted coax the MFJ-259b read 7.484.2 to 7.523 Mhz, 20.2 SWR, R=2 ohms, X=0. Seems like the velocity factor is considerably higher than what was stated to me by DX Eng.. The velocity factor is some where around 0.84401... as best I can figure it. So I guess that makes it 0.84 VF FWIW. Anyway, I have it figured that 55' 4 3/8" will do the trick for my 80 meter 4-Square at 3.750 Mhz. But why my RE analyzer went out today I don't have any idea. Back to the MFJ! Terry KI7M > On June 9, 2018 at 6:59 PM terry burge wrote: > > > Good point Wes. I will see if I can find a decent value of resistor. My > Rig Experts AA-170 was purchased because I did not trust the readings my > MFJ-259b was giving me while working on my hytower. Pretty penny for these > antenna analyzers. But I will bet if it won't do the stub frequency checks it > won't do the velocity factor and more. Did work pretty good for checking SWR > and feedpoint impedance on antennas like the hytower. Really liked it until > this. > > > Terry > > KI7M > > > > On June 9, 2018 at 5:11 PM Wes Stewart wrote: > > > > > > Since he said the coax was 75-ohm, a 75-ohm termination would be > > better. > > > > > > On 6/9/2018 5:07 PM, Richard (Rick) Karlquist wrote: > > > > As a sanity check, terminate the coax with a 50 ohm resistor > > and verify > > > > > > > that you have good coax. Flat line at 1:1 SWR, etc. > > > > > > Rick N6RK > > > > > > On 6/9/2018 4:57 PM, terry burge wrote: > > > > > > I don't know what is wrong here but I keep getting in > > > this situation where my > > > > > > > > > > typing starts running back over my writing. I > > > will try again to reply. > > > > > > > > > > > > Joel, > > > > > > > > I have tried all that the manual says without success. > > > > All I see is the > > > > horizontal solid and dashed lines of R and X. No > > > > indication of a resonance > > > > point anywhere from 1880 KHz up to 10,500 KHz. Go > > > > figure? At least my > > > > mfj-259b is working old as it may be. Rig Experts is > > > > going to get a nasty > > > > note I think. Disappointing, huh? > > > > > > > > > > > > Terry > > > > > > > > KI7M > > > > > > > > On June 9, 2018 at 2:54 PM Joel Harrison wrote: > > > > > > > > > > > > > Hi Terry, > > > > > > > > > > I replaced the 1/4 lines on my 80 meter 4 square > > > > > this past fall and used > > > > > my AA-170 to set the length with no problem. > > > > > > > > > > Just select "all" for the mode and set the freq > > > > > you're aiming for and then > > > > > trim the line until X equals zero with the far > > > > > end open. Should work fine. > > > > > I always calculate the length x VF then add a few > > > > > feet to start. > > > > > > > > > > 73 Joel W5ZN > > Hi guys and gals, > > > > > > > > > > > > > > > > > > > > > > I have got DX Engineering 75 ohm foam > > > > > coax to make the > > > > > > > > > > > > > > > > stubs/feeders for > > > > > > my Comtek 80 meter 4-Square and am finding > > > > > > some difficulty. > > > > > > Neither my > > > > > > MFJ-259B nor my Rig Experts AA-170 seem to > > > > > > indicate a 1/2 WL at > > > > > > 7500 KHz > > > > > > or a 1/4 WL at 3750 KHz? Or any frequency > > > > > > up or down from there. > > > > > > Seems to > > > > > > me the last time I did this a few years ago > > > > > > I didn't have a problem > > > > > > getting a 1/2 WL dip indicating a resonance > > > > > > location. But now I > > > > > > just don't > > > > > > get any indication of a resonance. > > > > > > > > > > > > > > > > > > DX Engineering said they had got some 75 > > > > > > ohm foam coax that > > > > > > instead of > > > > > > 0.84 VF was more like 0.80 down to 0.76 VF. > > > > > > But checking all the > > > > > > way down > > > > > > to 6000 KHz on 40 meters or 2500
Re: Topband: cutting coax stubs for 80 meter 4-square
I used a return loss bridge and measured a TEE fitting with a good 50 ohm load on one port the length of cable on the other side. The antenna analyzer will read a perfect 50 ohm match when the cable is 1/2 wavelength long. If the cable is an open quarter wave, your analyzer will show high VSWR or low return loss. keep in mind that you will see many bumps as you increase frequency and you get multiples of half waves and quarter waves. You want the lowest frequency VSWR null and that is a single half wave at that frequency. A half wave repeats the impedance, so an open half wave in coax will also look like a open at the TEE fitting and it is across the 50 ohm load so it still looks like a 50 ohm load. (low VSWR) Every open quarter wave coax reflects back as a short, and that makes the VSWR very poor. Dave K1wHS On 6/9/2018 7:55 PM, terry burge wrote: Hi guys and gals, I have got DX Engineering 75 ohm foam coax to make the stubs/feeders for my Comtek 80 meter 4-Square and am finding some difficulty. Neither my MFJ-259B nor my Rig Experts AA-170 seem to indicate a 1/2 WL at 7500 KHz or a 1/4 WL at 3750 KHz? Or any frequency up or down from there. Seems to me the last time I did this a few years ago I didn't have a problem getting a 1/2 WL dip indicating a resonance location. But now I just don't get any indication of a resonance. DX Engineering said they had got some 75 ohm foam coax that instead of 0.84 VF was more like 0.80 down to 0.76 VF. But checking all the way down to 6000 KHz on 40 meters or 2500 KHz on 80 meters fails. My test is to use either antenna analyzer with a PL-259 installed at one end and an open or a short at the other. I started with 57'7" of coax. Tried both with the coax in a roll and strung out. What am I doing wrong? Terry KI7M _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: cutting coax stubs for 80 meter 4-square
Good point Wes. I will see if I can find a decent value of resistor. My Rig Experts AA-170 was purchased because I did not trust the readings my MFJ-259b was giving me while working on my hytower. Pretty penny for these antenna analyzers. But I will bet if it won't do the stub frequency checks it won't do the velocity factor and more. Did work pretty good for checking SWR and feedpoint impedance on antennas like the hytower. Really liked it until this. Terry KI7M > On June 9, 2018 at 5:11 PM Wes Stewart wrote: > > > Since he said the coax was 75-ohm, a 75-ohm termination would be better. > > > On 6/9/2018 5:07 PM, Richard (Rick) Karlquist wrote: > > > > As a sanity check, terminate the coax with a 50 ohm resistor and > verify > > that you have good coax. Flat line at 1:1 SWR, etc. > > > > Rick N6RK > > > > On 6/9/2018 4:57 PM, terry burge wrote: > > > > > > > I don't know what is wrong here but I keep getting in > > this situation where my > > > typing starts running back over my writing. I will try again > > > to reply. > > > > > > > > > Joel, > > > > > > I have tried all that the manual says without success. All I > > > see is the > > > horizontal solid and dashed lines of R and X. No indication > > > of a resonance > > > point anywhere from 1880 KHz up to 10,500 KHz. Go figure? At > > > least my > > > mfj-259b is working old as it may be. Rig Experts is going to > > > get a nasty > > > note I think. Disappointing, huh? > > > > > > > > > Terry > > > > > > KI7M > > > > > > > > > > On June 9, 2018 at 2:54 PM Joel Harrison wrote: > > > > > > > > > > > > Hi Terry, > > > > > > > > I replaced the 1/4 lines on my 80 meter 4 square this > > > > past fall and used > > > > my AA-170 to set the length with no problem. > > > > > > > > Just select "all" for the mode and set the freq you're > > > > aiming for and then > > > > trim the line until X equals zero with the far end > > > > open. Should work fine. > > > > I always calculate the length x VF then add a few feet > > > > to start. > > > > > > > > 73 Joel W5ZN > > > > > > Hi guys and gals, > > > > > > > > > > > > > > > > > > > > > > > I have got DX Engineering 75 ohm foam > > > > coax to make the > > > > > stubs/feeders for > > > > > my Comtek 80 meter 4-Square and am finding some > > > > > difficulty. > > > > > Neither my > > > > > MFJ-259B nor my Rig Experts AA-170 seem to > > > > > indicate a 1/2 WL at > > > > > 7500 KHz > > > > > or a 1/4 WL at 3750 KHz? Or any frequency up or > > > > > down from there. > > > > > Seems to > > > > > me the last time I did this a few years ago I > > > > > didn't have a problem > > > > > getting a 1/2 WL dip indicating a resonance > > > > > location. But now I > > > > > just don't > > > > > get any indication of a resonance. > > > > > > > > > > > > > > > DX Engineering said they had got some 75 ohm foam > > > > > coax that > > > > > instead of > > > > > 0.84 VF was more like 0.80 down to 0.76 VF. But > > > > > checking all the > > > > > way down > > > > > to 6000 KHz on 40 meters or 2500 KHz on 80 meters > > > > > fails. > > > > > > > > > > > > > > > My test is to use either antenna analyzer with a > > > > > PL-259 installed > > > > > at one > > > > > end and an open or a short at the other. I > > > > > started with 57'7" of > > > > > coax. > > > > > Tried both with the coax in a roll and strung > > > > > out. What am I doing > > > > > wrong? > > > > > > > > > > > > > > > Terry > > > > > > > > > > KI7M > > > > > > > > > > > > > > > _ > > > > > Topband Reflector Archives - > > > > > http://www.contesting.com/_topband > > > > > > > > > > > > > > > > > > > > > > > > > _ > > > > Topband Reflector Archives - > > > > http://www.contesting.com/_topband > > > > > > > > > > > _ > > > Topband Reflector Archives - > > > http://www.contesting.com/_topband > > > > > > > > _ > > Topband Reflector Archives -
Re: Topband: cutting coax stubs for 80 meter 4-square
Since he said the coax was 75-ohm, a 75-ohm termination would be better. On 6/9/2018 5:07 PM, Richard (Rick) Karlquist wrote: As a sanity check, terminate the coax with a 50 ohm resistor and verify that you have good coax. Flat line at 1:1 SWR, etc. Rick N6RK On 6/9/2018 4:57 PM, terry burge wrote: I don't know what is wrong here but I keep getting in this situation where my typing starts running back over my writing. I will try again to reply. Joel, I have tried all that the manual says without success. All I see is the horizontal solid and dashed lines of R and X. No indication of a resonance point anywhere from 1880 KHz up to 10,500 KHz. Go figure? At least my mfj-259b is working old as it may be. Rig Experts is going to get a nasty note I think. Disappointing, huh? Terry KI7M On June 9, 2018 at 2:54 PM Joel Harrison wrote: Hi Terry, I replaced the 1/4 lines on my 80 meter 4 square this past fall and used my AA-170 to set the length with no problem. Just select "all" for the mode and set the freq you're aiming for and then trim the line until X equals zero with the far end open. Should work fine. I always calculate the length x VF then add a few feet to start. 73 Joel W5ZN > > Hi guys and gals, I have got DX Engineering 75 ohm foam coax to make the stubs/feeders for my Comtek 80 meter 4-Square and am finding some difficulty. Neither my MFJ-259B nor my Rig Experts AA-170 seem to indicate a 1/2 WL at 7500 KHz or a 1/4 WL at 3750 KHz? Or any frequency up or down from there. Seems to me the last time I did this a few years ago I didn't have a problem getting a 1/2 WL dip indicating a resonance location. But now I just don't get any indication of a resonance. DX Engineering said they had got some 75 ohm foam coax that instead of 0.84 VF was more like 0.80 down to 0.76 VF. But checking all the way down to 6000 KHz on 40 meters or 2500 KHz on 80 meters fails. My test is to use either antenna analyzer with a PL-259 installed at one end and an open or a short at the other. I started with 57'7" of coax. Tried both with the coax in a roll and strung out. What am I doing wrong? Terry KI7M _ Topband Reflector Archives - http://www.contesting.com/_topband > _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: cutting coax stubs for 80 meter 4-square
As a sanity check, terminate the coax with a 50 ohm resistor and verify that you have good coax. Flat line at 1:1 SWR, etc. Rick N6RK On 6/9/2018 4:57 PM, terry burge wrote: I don't know what is wrong here but I keep getting in this situation where my typing starts running back over my writing. I will try again to reply. Joel, I have tried all that the manual says without success. All I see is the horizontal solid and dashed lines of R and X. No indication of a resonance point anywhere from 1880 KHz up to 10,500 KHz. Go figure? At least my mfj-259b is working old as it may be. Rig Experts is going to get a nasty note I think. Disappointing, huh? Terry KI7M On June 9, 2018 at 2:54 PM Joel Harrison wrote: Hi Terry, I replaced the 1/4 lines on my 80 meter 4 square this past fall and used my AA-170 to set the length with no problem. Just select "all" for the mode and set the freq you're aiming for and then trim the line until X equals zero with the far end open. Should work fine. I always calculate the length x VF then add a few feet to start. 73 Joel W5ZN > > Hi guys and gals, I have got DX Engineering 75 ohm foam coax to make the stubs/feeders for my Comtek 80 meter 4-Square and am finding some difficulty. Neither my MFJ-259B nor my Rig Experts AA-170 seem to indicate a 1/2 WL at 7500 KHz or a 1/4 WL at 3750 KHz? Or any frequency up or down from there. Seems to me the last time I did this a few years ago I didn't have a problem getting a 1/2 WL dip indicating a resonance location. But now I just don't get any indication of a resonance. DX Engineering said they had got some 75 ohm foam coax that instead of 0.84 VF was more like 0.80 down to 0.76 VF. But checking all the way down to 6000 KHz on 40 meters or 2500 KHz on 80 meters fails. My test is to use either antenna analyzer with a PL-259 installed at one end and an open or a short at the other. I started with 57'7" of coax. Tried both with the coax in a roll and strung out. What am I doing wrong? Terry KI7M _ Topband Reflector Archives - http://www.contesting.com/_topband > _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: cutting coax stubs for 80 meter 4-square
I don't know what is wrong here but I keep getting in this situation where my typing starts running back over my writing. I will try again to reply. Joel, I have tried all that the manual says without success. All I see is the horizontal solid and dashed lines of R and X. No indication of a resonance point anywhere from 1880 KHz up to 10,500 KHz. Go figure? At least my mfj-259b is working old as it may be. Rig Experts is going to get a nasty note I think. Disappointing, huh? Terry KI7M > On June 9, 2018 at 2:54 PM Joel Harrison wrote: > > > Hi Terry, > > I replaced the 1/4 lines on my 80 meter 4 square this past fall and used > my AA-170 to set the length with no problem. > > Just select "all" for the mode and set the freq you're aiming for and then > trim the line until X equals zero with the far end open. Should work fine. > I always calculate the length x VF then add a few feet to start. > > 73 Joel W5ZN > > > > Hi guys and gals, > > > > > > I have got DX Engineering 75 ohm foam coax to make the > > stubs/feeders for > > my Comtek 80 meter 4-Square and am finding some difficulty. Neither > > my > > MFJ-259B nor my Rig Experts AA-170 seem to indicate a 1/2 WL at > > 7500 KHz > > or a 1/4 WL at 3750 KHz? Or any frequency up or down from there. > > Seems to > > me the last time I did this a few years ago I didn't have a problem > > getting a 1/2 WL dip indicating a resonance location. But now I > > just don't > > get any indication of a resonance. > > > > > > DX Engineering said they had got some 75 ohm foam coax that instead > > of > > 0.84 VF was more like 0.80 down to 0.76 VF. But checking all the > > way down > > to 6000 KHz on 40 meters or 2500 KHz on 80 meters fails. > > > > > > My test is to use either antenna analyzer with a PL-259 installed > > at one > > end and an open or a short at the other. I started with 57'7" of > > coax. > > Tried both with the coax in a roll and strung out. What am I doing > > wrong? > > > > > > Terry > > > > KI7M > > > > > > _ > > Topband Reflector Archives - http://www.contesting.com/_topband > > > > > > _ > Topband Reflector Archives - http://www.contesting.com/_topband > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: cutting coax stubs for 80 meter 4-square
Hi Terry, I replaced the 1/4 lines on my 80 meter 4 square this past fall and used my AA-170 to set the length with no problem. Just select "all" for the mode and set the freq you're aiming for and then trim the line until X equals zero with the far end open. Should work fine. I always calculate the length x VF then add a few feet to start. 73 Joel W5ZN > Hi guys and gals, > > > I have got DX Engineering 75 ohm foam coax to make the stubs/feeders for > my Comtek 80 meter 4-Square and am finding some difficulty. Neither my > MFJ-259B nor my Rig Experts AA-170 seem to indicate a 1/2 WL at 7500 KHz > or a 1/4 WL at 3750 KHz? Or any frequency up or down from there. Seems to > me the last time I did this a few years ago I didn't have a problem > getting a 1/2 WL dip indicating a resonance location. But now I just don't > get any indication of a resonance. > > > DX Engineering said they had got some 75 ohm foam coax that instead of > 0.84 VF was more like 0.80 down to 0.76 VF. But checking all the way down > to 6000 KHz on 40 meters or 2500 KHz on 80 meters fails. > > > My test is to use either antenna analyzer with a PL-259 installed at one > end and an open or a short at the other. I started with 57'7" of coax. > Tried both with the coax in a roll and strung out. What am I doing wrong? > > > Terry > > KI7M > > > _ > Topband Reflector Archives - http://www.contesting.com/_topband > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: cutting coax stubs for 80 meter 4-square
Ok Terry, well 1/2 wave at 7234kc will = 1/4 wave at 3617kc, so trim until u get near 7500kc and cut all lines that length and u should be ok. Back in the 1980s when I built my 4 square, I used a noise bridge to build my lines. Ed KG4W On 6/9/2018 5:19 PM, terry burge wrote: Hi Ed, Unfortunately I don't get any indication per the Rig Experts manual with an open. The R/X just does not get any indication from 1982Khz all the way to 10,500+ KHz. On my MFJ-259B (old one) with a short I get at 7.234 Mhz (or about) R=1 and X=0. Suspect the R indicates the short of course but the X=0 is what I am looking for. I'm going to start cutting a little bit at a time and see what happens. I have already verified the coax is not shorted with my ohm meter till I put the gator on it so the coax appears alright. I am wondering just how 'critical' is getting the lengths exact? One thing I did not quite understand was why the RE said to cut for 20% lower? Terry KI7M On June 9, 2018 at 2:09 PM Ed Hughes wrote: Hi Terry, see page 16 of this site https://www.rigexpert.com/files/manuals/aa170/aa-170-manual.pdf when looking for a 1/4 wave, leave the far end of the coax under test open. when looking for a 1/2 wave, short the far end of the coax under test. Your 57'7" pc of would be 1/4 wave at 3750 if the vf is 87.77 at vf .76 = 49.85 ft at vf .80 = 52.48 ft at vf .84 = 55.10 ft Set your rig expert on freq 3750 and have it in the RX mode and you should see something that makes sense. Good Luck Ed KG4W On 6/9/2018 3:55 PM, terry burge wrote: Hi guys and gals, I have got DX Engineering 75 ohm foam coax to make the stubs/feeders for my Comtek 80 meter 4-Square and am finding some difficulty. Neither my MFJ-259B nor my Rig Experts AA-170 seem to indicate a 1/2 WL at 7500 KHz or a 1/4 WL at 3750 KHz? Or any frequency up or down from there. Seems to me the last time I did this a few years ago I didn't have a problem getting a 1/2 WL dip indicating a resonance location. But now I just don't get any indication of a resonance. DX Engineering said they had got some 75 ohm foam coax that instead of 0.84 VF was more like 0.80 down to 0.76 VF. But checking all the way down to 6000 KHz on 40 meters or 2500 KHz on 80 meters fails. My test is to use either antenna analyzer with a PL-259 installed at one end and an open or a short at the other. I started with 57'7" of coax. Tried both with the coax in a roll and strung out. What am I doing wrong? Terry KI7M _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: cutting coax stubs for 80 meter 4-square
Hi Ed, Unfortunately I don't get any indication per the Rig Experts manual with an open. The R/X just does not get any indication from 1982Khz all the way to 10,500+ KHz. On my MFJ-259B (old one) with a short I get at 7.234 Mhz (or about) R=1 and X=0. Suspect the R indicates the short of course but the X=0 is what I am looking for. I'm going to start cutting a little bit at a time and see what happens. I have already verified the coax is not shorted with my ohm meter till I put the gator on it so the coax appears alright. I am wondering just how 'critical' is getting the lengths exact? One thing I did not quite understand was why the RE said to cut for 20% lower? Terry KI7M > On June 9, 2018 at 2:09 PM Ed Hughes wrote: > > > Hi Terry, see page 16 of this site > https://www.rigexpert.com/files/manuals/aa170/aa-170-manual.pdf > > when looking for a 1/4 wave, leave the far end of the coax under test open. > when looking for a 1/2 wave, short the far end of the coax under test. > > Your 57'7" pc of would be 1/4 wave at 3750 if the vf is 87.77 > at vf .76 = 49.85 ft > at vf .80 = 52.48 ft > at vf .84 = 55.10 ft > > Set your rig expert on freq 3750 and have it in the RX mode and you > should see something that makes sense. > > Good Luck > Ed > KG4W > On 6/9/2018 3:55 PM, terry burge wrote: > > Hi guys and gals, > > > > > > I have got DX Engineering 75 ohm foam coax to make the stubs/feeders for my > > Comtek 80 meter 4-Square and am finding some difficulty. Neither my > > MFJ-259B nor my Rig Experts AA-170 seem to indicate a 1/2 WL at 7500 KHz or > > a 1/4 WL at 3750 KHz? Or any frequency up or down from there. Seems to me > > the last time I did this a few years ago I didn't have a problem getting a > > 1/2 WL dip indicating a resonance location. But now I just don't get any > > indication of a resonance. > > > > > > DX Engineering said they had got some 75 ohm foam coax that instead of 0.84 > > VF was more like 0.80 down to 0.76 VF. But checking all the way down to > > 6000 KHz on 40 meters or 2500 KHz on 80 meters fails. > > > > > > My test is to use either antenna analyzer with a PL-259 installed at one > > end and an open or a short at the other. I started with 57'7" of coax. > > Tried both with the coax in a roll and strung out. What am I doing wrong? > > > > > > Terry > > > > KI7M > > > > > > _ > > Topband Reflector Archives - http://www.contesting.com/_topband > > _ > Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: cutting coax stubs for 80 meter 4-square
Hi Terry, see page 16 of this site https://www.rigexpert.com/files/manuals/aa170/aa-170-manual.pdf when looking for a 1/4 wave, leave the far end of the coax under test open. when looking for a 1/2 wave, short the far end of the coax under test. Your 57'7" pc of would be 1/4 wave at 3750 if the vf is 87.77 at vf .76 = 49.85 ft at vf .80 = 52.48 ft at vf .84 = 55.10 ft Set your rig expert on freq 3750 and have it in the RX mode and you should see something that makes sense. Good Luck Ed KG4W On 6/9/2018 3:55 PM, terry burge wrote: Hi guys and gals, I have got DX Engineering 75 ohm foam coax to make the stubs/feeders for my Comtek 80 meter 4-Square and am finding some difficulty. Neither my MFJ-259B nor my Rig Experts AA-170 seem to indicate a 1/2 WL at 7500 KHz or a 1/4 WL at 3750 KHz? Or any frequency up or down from there. Seems to me the last time I did this a few years ago I didn't have a problem getting a 1/2 WL dip indicating a resonance location. But now I just don't get any indication of a resonance. DX Engineering said they had got some 75 ohm foam coax that instead of 0.84 VF was more like 0.80 down to 0.76 VF. But checking all the way down to 6000 KHz on 40 meters or 2500 KHz on 80 meters fails. My test is to use either antenna analyzer with a PL-259 installed at one end and an open or a short at the other. I started with 57'7" of coax. Tried both with the coax in a roll and strung out. What am I doing wrong? Terry KI7M _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: cutting coax stubs for 80 meter 4-square
Hi guys and gals, I have got DX Engineering 75 ohm foam coax to make the stubs/feeders for my Comtek 80 meter 4-Square and am finding some difficulty. Neither my MFJ-259B nor my Rig Experts AA-170 seem to indicate a 1/2 WL at 7500 KHz or a 1/4 WL at 3750 KHz? Or any frequency up or down from there. Seems to me the last time I did this a few years ago I didn't have a problem getting a 1/2 WL dip indicating a resonance location. But now I just don't get any indication of a resonance. DX Engineering said they had got some 75 ohm foam coax that instead of 0.84 VF was more like 0.80 down to 0.76 VF. But checking all the way down to 6000 KHz on 40 meters or 2500 KHz on 80 meters fails. My test is to use either antenna analyzer with a PL-259 installed at one end and an open or a short at the other. I started with 57'7" of coax. Tried both with the coax in a roll and strung out. What am I doing wrong? Terry KI7M _ Topband Reflector Archives - http://www.contesting.com/_topband
